Stress relief cracking in high strength structural steel BS 4360 grade 55F

Abstract

The stress relief cracking susceptibility of a commercial cast of BS 4360 55F, a high strength structural steel, has been investigated by short term creep rupture testing of crossweld specimens. The weld was made with a heat input of 1·75 kJ mm⁻¹, which is typical of that encountered during fabrication. The creep specimens fractured in the coarse grained heat affected zone with low deformation over a wide range of test conditions. In all instances failure was by intergranular cracking at prior austenite grain boundaries, generally by the formation of creep cavities. This indicates that the steel is susceptible to stress relief cracking for the high welding heat inputs used. Special precautions may be necessary when welding high strength steels of this type when postweld heat treatment is specified.

MST/745